Despite interesting results from the many studies on otters, we are left with the main message that very little is yet known about these animals. Several questions need to be addressed urgently, to cover important conservation problems or because of more academic interest, but usually for both reasons. For some species we know next to nothing about ecology and behaviour, but even for those that have had some attention, we still know little about actual numbers over larger areas, about population sizes, and about changes in areas where previous estimates have been made.
For all, the genetic composition of populations needs further study, to determine their variability and differences between regions. We need to know what are the barriers between populations, and whether there are differences that should be kept in mind when considering transplantations. Given the limited genetic diversity within populations, one wants to know about dangers associated with inbreeding. DNA techniques are opening new doors here, as well as providing new means of assessing otter numbers and social organizations.
The processes of population change still need further elucidation. For instance, what is the cause of the increase in Eurasian otter mortality with age? How and why is the oestrus cycle synchronized with the seasons in some regions, and apparently random elsewhere? What is the profitability of foraging in various areas, taking into account success rates and prey types, as well as water temperatures? Much more information is required on populations of relevant fish species, their population dynamics, fluctuations and responses to predation. The characteristics of fish populations will be crucial to otters everywhere, and a dedicated, interdisciplinary approach to the role of fish populations is much needed.
More information is required on intraspecific as well as interspecific variation in the spatial organization of otters, and underlying environmental differences. For instance, how is L. lutra organized in countries in south-east Asia, where it lives in totally different vegetation types, where it has to compete with other species of otters, and where it may be subject to much higher predation? Such questions of intraspecific differences need to be answered in order to establish the flexibility of a species in the face of environmental change. What is the relationship between predation on North American river otters and their organization of male packs and solitary females? Similar questions should be asked for other species of otters; as just one example, what causes the spotted-necked otter to live in large, diurnally active, packs in Lake Victoria, and as nocturnal, solitary individuals in streams of South Africa?
Perhaps the most immediate need is for an understanding of the relationship between sea otters and killer whales, and how this can possibly be managed. There are other direct conservation problems: how do Eurasian otters respond to transplantation (reintroduction), how do populations respond to increases or decreases in their food supply, what are the pollutant levels in otters from stable, or increasing or decreasing populations? One could add many more such questions, but even the most basic problems in the ecology and behaviour of all but two or three species of otter are still open. A great deal of fascinating research has yet to be done to serve as a solid basis for conservation management.
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